136 OTHER FACTORS OP EVOLUTION 



variation generally. These, or at all events the majority of them, 

 appear to be local effects not dating from the germ-plasm at all, 

 but from the soma, and that often at a comparatively late stage of 

 its development. The occurrence of such mere local changes was 

 fully recognised by Spencer as not necessarily taking their origin 

 in the germ-plasm, since when speaking of his physiological units 

 he said (I, p. 369) they must be presumed to have " such natures 

 that while a minute modification, representing some small change 

 of local structure, is inoperative on the proclivities of the units 

 throughout the rest of the system, it becomes operative in the units 

 which fall into the locality where that change occurs." And in 

 regard to what is known as " irregular peloria " Maxwell Masters ' 

 makes the definite statement that this form of " peloria is evidently 

 not congenital, but occurs at a more or less advanced stage of 

 development." 



Bud-variations generally are now known to be excessively 

 numerous. As far back as 1895, according to Prof. Bailey of 

 Cornell University, no less than 300 of such bud-sports were 

 known and actually under cultivation in the United States. And 

 as showing that these bud-variations and germinal-variations are 

 essentially similar in kind, though the change in the one case 

 takes place in the soma and, in the other, in the germ-plasm, there 

 is the fact, as Lloyd Andriezen points out,^ that " selection can be 

 practised for the improvement and definiteness of forms originating 

 by either means." 



There seems, therefore, absolutely no room for doubt that local 

 variations may take their origin in the soma and may be perpetu- 

 ated, selected and increased therein, in the form of bud-variations. 

 It seems equally clear that in other cases we may have actual new 

 species of plants arising by ' mutation,' as a result of quasi-' spon- 

 taneous ' changes, either in the germ-plasm or in the soma ; and 

 that in other cases, still under the influence of altered external 

 conditions — whether acting primarily upon the soma or upon the 

 germ-plasm or concurrently — we may find variations arising in 

 plants and animals which are capable of being inherited and 

 transmitted to their progeny. The evidence, as we have seen, is 

 equally clear also in favour of the heritable effects of use and disuse. 



There is thus reason to believe that we have other most impor- 



' " Vegetable Teratology," p. 229. 



» " The Problem of Heredity, &c." " Jrnl. of Mental Science," January, 1905, 

 p. 20. 



